As disclosed in Japanese Patent Laid-Open HEI No. 58-101206, an electromagnetic valve apparatus has been conventionally employed as an intake valve of an internal combustion engine. In this conventional internal combustion engine, the electromagnetic valve apparatus comprises an intake valve for opening and closing an intake port and an electromagnetic driving apparatus for driving the intake valve. The intake valve and the electromagnetic driving apparatus, which constitute the electromagnetic valve apparatus, are both integrated into the internal combustion engine.
The electromagnetic driving apparatus is coupled to a control device disposed outside the engine. At a predetermined timing based on an operating condition of the engine, the control device supplies driving power to the electromagnetic driving apparatus to drive the intake valve between an open position and a closed position thereof. This construction allows the intake valve to be opened or closed at a predetermined timing corresponding to an operating condition of the internal combustion engine.
In this engine, the control device must be equipped with a driver including power elements or switching elements for supplying driving power to the electromagnetic driving apparatus and, in supplying this driving power, the driver generate heat. Also, the driver operate suitably only below a heat resistant temperature thereof. Hence, it is necessary to ensure sufficient cooling capacity where this driver is mounted.
For example, it is known to use a heat sink to cool the driver. In the aforementioned conventional internal combustion engine, the driver can be cooled by a heat sink disposed inside the control device. However, driving the intake valve requires that the electromagnetic valve be supplied with a relatively large driving power. Hence, a comparatively large heat sink must be employed in order to ensure that the driver is sufficiently cooled.
However, it is very difficult to mount a control device containing such a large heat sink on the vehicle. Thus, this engine provides a problem with either the cooling capacity required by the driver or with mounting of the device in the engine.